View MIC28303-2YMP_8516641.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mic28303 50v 3a power module hyper speed control? family hyper speed control and any capacitor are trademark s of micrel, inc . hyperlight load is a registered trademark of micrel, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944 - 0800 ? fax + 1 (408) 474 - 1000 ? http://www.micrel.com february 12, 2015 revision 1.0 general description micrel?s mic28303 is synchronous step - down regulator module, featuring a unique adaptive on - time control architecture. the module incorporates a dc/ dc controller, power mosfets, bootstrap diode, bootstrap capacitor and an inductor in a single package. the mic28303 operates over an input supply range from 4.5v to 50v and can be used to supply up to 3a of output current. the output voltage is adjustable down to 0.8v with a guaranteed accuracy of 1%. the device operates with programmable switching frequency from 200khz to 600khz. the mic28303 - 1 uses micrel?s hyperlight load ? architecture for improved efficiency at light loads. the mic28303 - 2 uses micrel ?s hyper speed control ? for ultra - fast transient response. the mic28303 offers a full suite of protection features . these include under voltage lockout, internal soft - start , fold back current limit, ?hiccup? mode short - circuit protection , and thermal shutdow n. datasheets and support documentation are available on micrel?s web site at : www.micrel.com . features ? easy to use ? stable with low - esr ceramic output capacitor ? no compensation and no inductor to choose ? 4.5v to 50v inp ut voltage ? single - supply operation ? power g ood (pg) output ? low radiat ed emission (emi) per en55022, c lass b ? adjustable current limit ? adjustable output voltage from 0. 9 v to 24v (also limited by duty cycle) ? 2 00khz to 600khz , programmable switching frequency ? supports safe start - up into a pre - biased output ? ? 40 c to +125 c junction temperature range ? available in 64 - pin, 12mm 12mm 3mm qfn package applications ? distributed power systems ? industrial, medical, telecom, and automotive typical application
micrel, inc. mic28303 february 12, 2015 2 revision 1.0 ordering information part number switching frequency features package junction temperature range lead finish mic28303 -1 ym p 2 00khz to 600khz hyperlight load 64- pin 12mm 12mm qfn ? 40c to +125c pb - free mic 28303- 2ym p 2 00khz to 600khz hyper speed control 64- pin 12mm 12mm qfn ? 40c to +125c pb - free pin configuration 64- pin 12mm 12mm qfn ( mp ) (top view) pin description pin number pin name pin function 1, 2, 3, 54, 64 gnd analog g round. ground for internal controller and feedback resistor network. the analog ground return path should be separate from the power ground (pgnd) return path. 4 ilim current limit s etting. connect a resistor from sw (pin 6 ) to ilim to set the over - current threshold for the converter. 5, 60 vin supply voltage for c ontroller. the vin operating voltage range is from 4.5v to 50v . a 0.47 f ceramic capacitor from vin (pin 60) to gnd is required for decoupling. pin 5 should be externally co nnected to either pvin or pin 60 on pcb. 6, 40 to 48, 51 sw switch node and curr ent - sense input. high current output driver return. the sw pin connects directly to the switch node. due to the high - speed switching on this pin, the sw pin should be routed away from sensitive nodes. the sw pin also senses the current by monitoring the vo ltage across the low - side mosfet during off time.
micrel, inc. mic28303 february 12, 2015 3 revision 1.0 pin description (continued) pin number pin name pin function 7, 8 freq switching frequency adjust input. leaving this pin open will set the switching frequency to 600khz. alternatively , a resistor from this pin to ground can be used to lower the switching frequency. 9 to 13 pgnd power ground. pgnd is the return path for the buck converter power stage. the pgnd pin connects to the sources of low - side n - channel external mosfet, the negat ive terminals of input capacitors, and the negative terminals of output capacitors. the return path for the power ground should be as small as possible and separate from the analog ground (gnd) return path. 14 to 22 pvin power input voltage. connection to the drain of the internal high - side power mosfet. 23 to 38 vout output voltage. connection with the internal inductor, the output capacitor should be connected from this pin to pgnd as close to the module as possible. 39 nc no connection. leave it flo ating. 49, 50 anode anode bootstrap diode input . anode connection of internal bootstrap diode . t his pin should be connected to the pvdd pin. 52, 53 bstc bootstrap capacitor . connection to the internal bootstrap capacitor. leave floating, no connect. 55, 56 bstr bootstrap resistor . connection to the internal bootstrap resistor and high - side power mosfet drive circuitry. leave floating, no connect. 57 fb feedback inpu t . input to the transconductance amplifier of the control loop. the fb pin is regulate d to 0.8v. a resistor divider connecting the feedback to the output is used to set the desired output voltage. 58 pgood power good output . open - drain o utput . a n external pull - up resistor to external power rails is required. 59 en enable input . a logic signal to enable or disable the buck converter operation. the en pin is cmos compatible. logic high enables the device, logic low shut s down the regulator. in the disable mode, the input supply current for the device is minimized to 4 a typically. do not pull en to pvdd. 61, 62 pvdd internal +5v linear regulator output . p vdd is the int ernal supply bus for the device . in the applications with vin < +5.5v, p vdd should be tied to vin to by - pass the linear regulator. 63 nc no connection . leave it floating.
micrel, inc. mic28303 february 12, 2015 4 revision 1.0 absolute maximum ratings ( 1 ) p vin , v in to p gnd ...................................... ? 0.3v to +5 6v pvdd , v anode to pgnd .................................. ? 0.3v to +6v v sw , v freq , v ilim , v en ........................ ? 0.3v to (pvin +0.3v) v bstc/bstr to v sw ................................................ ? 0.3v to 6v v bstc/bstr to pgnd .......................................... ? 0.3v to 56 v v fb , v pg to pgnd ......................... ? 0.3v to (pvdd + 0.3v) pgnd to agnd ............................................ ? 0.3v to +0.3v junction temperature .............................................. +150c storage temperature (t s ) ......................... ? 65 c to +150 c l ead temperature (soldering, 10s) ............................ 260c esd rating ( 3) ................................................. esd sensitive operating ratings ( 2 ) supply voltage ( pvin, v in ) .............................. 4.5v to 50v enable input (v en ) ................................................. 0v to v in v sw , v feq , v ilim , v en .............................................. 0v to v in power good (v pgood )..??????..??? ... 0v to pv dd junction temperature (t j ) ........................ ? 40 c to +125 c junction th ermal resistance 12mm 12mm qfn - 64 ( ja ) ............................ 20c/w 12mm 12mm qfn - 64 ( jc ) ............................... 5c/w electrical characteristics ( 4 ) pvin = vin = 12v, v out = 5v, v bst ? v sw = 5v; t a = 25c, unless noted. bold values indicate ? j ??& parameter condition min . typ . max . units power supply input input voltage range (p vin , v in ) 4.5 5 0 v controller supply current ( 5 ) current into pin 60; v fb = 1.5v ( mic28303 -1) 0.4 0.75 ma current into pin 60;v fb = 1.5v ( mic28303 -2) 2.1 3 current into pin 60;v en = 0v 0.1 10 a operating current i out = 0a ( mic28303 -1) 0.7 ma i out = 0a ( mic28303 -2) 27 shutdown supply current p vin = v in = 12v, v en = 0v 4 a pvdd supply ( 5 ) pvdd output voltage vin = 7v to 50v , i pvdd = 10ma 4.8 5.2 5.4 v pvdd uvlo threshold pvdd rising 3.8 4.2 4. 7 v pvdd uvlo hysteresis 400 mv load regulation i pvdd = 0 to 40ma 0.6 2 3.6 % reference ( 5 ) feedback reference voltage t j = 25c (1.0%) 0.792 0.8 0.808 v ? j ??&? 0.784 0.8 0.816 fb bias current v fb = 0.8v 5 500 na notes: 1. exceeding the absolute maximum ratings may damage the device. 2. the device is not guaranteed to function outside its operating ratings. 3. devices are esd sensitive. handling precautions are recommended. human body model, 1.5k in series with 100pf. 4. specification for packaged product only. 5. i c tested prior to assembly.
micrel, inc. mic28303 february 12, 2015 5 revision 1.0 electrical characteristics ( 4 ) (continued) pvin = vin = 12v, v out = 5v, v bst ? v sw = 5v; t a = 25c, unless noted. bold values indicate ? j ??& parameter condition min . typ . max . units enable control en logic level high 1.8 v en logic level low 0.6 v en hysteresis 200 mv en bias current v en = 12v 5 2 0 a oscillator switching frequency freq pin = open 400 600 750 khz rfreq = 100k (freq pin -to - gnd ) 300 maximum duty cycle 85 % minimum duty cycle v fb > 0.8v 0 % minimum off - time 140 200 260 ns soft - start ( 5 ) soft - start time 5 ms short - circuit protection ( 5 ) current - limit threshold (v cl ) v fb = 0.79v ? 30 ? 14 0 mv short - circuit threshold v fb = 0v ? 23 ? 7 9 mv current - limit source current v fb = 0.79v 60 80 100 a short - circuit source current v fb = 0v 27 36 47 a leakage sw, bstr leakage current 50 a power good ( 5 ) power good threshold voltage sweep v fb from low -to - high 85 90 95 %v out power good hysteresis sweep v fb from high - to - low 6 %v out power good delay time sweep v fb from low -to - high 100 s power good low voltage v fb < 90% x v nom , i pg = 1ma 70 200 mv thermal protection overt emperature shutdown t j rising 160 c overt emperature shutdown hysteresis 4 c
micrel, inc. mic28303 february 12, 2015 6 revision 1.0 electrical characteristics ( 4 ) (continued) pvin = vin = 12v, v out = 5v, v bst ? v sw = 5v; t a = 25c, unless noted. bold values indicate ? j ??& parameter condition min . typ . max . units output characteristic output voltage ripple i out = 3a 16 mv line regulation pvin = v in = 7v to 50v , i out = 3a 0.36 % load regulation i out = 0a to 3a pvin= v in =12v ( mic28303 -1) 0.75 % i out = 0a to 3a pvin= v in =12v ( mic28303 -2) 0.05 output voltage deviation from load step i out from 0a to 3a at 5a/ s ( mic28303 - 1) 400 mv i out from 3a to 0a at 5a/ s ( mic28303 - 1) 500 i out from 0a to 3a at 5a/ s ( mic28303 - 2) 400 i out from 3a to 0a at 5a/ s ( mic28303 - 2) 500
micrel, inc. mic28303 february 12, 2015 7 revision 1.0 typical characteristics ? 275khz switching frequency table 1 . recommended component values for 275khz switching frequency v out vin r3 (r inj ) r19 r15 r1 (top feedback resistor ) r11 (bottom feedback resistor ) c10 (c inj ) c12 (c ff ) c out 5v 7v to 18 v 16.5k 75k 3.57k n 1.9 n 0.1 f 2.2nf 2x 47f /6.3v 5v 18 v to 50v 39.2 k 75k 3.57k n 1.9 n 0.1 f 2.2nf 2x 47f /6.3v 3.3v 5v to 18 v 16.5k 75k 3.57k n 3.24 n 0.1 f 2.2nf 2x 47f /6.3v 3.3v 18 v to 50v 39.2 k 75k 3.57k n 3.24 n 0.1 f 2.2nf 2x 47f /6.3v 50 55 60 65 70 75 80 85 90 95 100 0 0.5 1 1.5 2 2.5 3 efficiency (%) output current (a) efficiency vs. output current (mic28303 - 1) v out = 5v f sw = 275khz 24vin 12vin 36vin 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 efficiency (%) output current (a) efficiency vs. output current (mic28303 - 2) v out = 5v f sw = 275khz 24vin 12vin 36vin 0 1 2 3 25 40 55 70 85 100 115 load current (a) maximum ambient temperature ( c) thermal derating (mic28303 - 2) v out = 5v f sw = 275khz t j_max = 125 c vin = 12v vin = 24v
micrel, inc. mic28303 february 12, 2015 8 revision 1.0 typical characteristics 0.00 0.40 0.80 1.20 1.60 2.00 5 10 15 20 25 30 35 40 45 50 supply current (ma) input voltage (v) vin operating supply current vs. input voltage (mic28303 - 1) v out = 5v i out = 0a f sw = 600khz -1.0% 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 7 12 17 22 27 32 37 42 47 total regulation (%) input voltage (v) output regulation vs. input voltage (mic28303 - 1) v out = 5.0v i out = 0a to 3a f sw = 600khz 4.90 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5 10 15 20 25 30 35 40 45 50 output voltage (v) input voltage (v) output voltage vs. input voltage (mic28303 - 1) v out = 5v i out = 0a f sw = 600khz 0.00 0.40 0.80 1.20 1.60 2.00 -50 -25 0 25 50 75 100 125 supply current (ma) temperature ( c) vin operating supply current vs. temperature (mic28303 - 1) vin = 12v v out = 5.0v i out = 0a f sw = 600khz 0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2% -50 -25 0 25 50 75 100 125 load regulation (%) temperature ( c) load regulation vs. temperature (mic28303 - 1) vin = 12v v out = 5.0v i out = 0a to 3a f sw = 600khz -0.6% -0.5% -0.4% -0.3% -0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8% -50 -25 0 25 50 75 100 125 line regulation (%) temperature ( c) line regulation vs. temperature (mic28303 - 1) vin = 7v to 50v v out = 5.0v i out = 0a f sw = 600khz -0.6% -0.5% -0.4% -0.3% -0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8% -50 -25 0 25 50 75 100 125 line regulation (%) temperature ( c) line regulation vs. temperature (mic28303 - 1) vin = 7v to 50v v out = 5.0v i out = 3a f sw = 600khz -3.0% -2.5% -2.0% -1.5% -1.0% -0.5% 0.0% 0.5% 1.0% 0.0 0.5 1.0 1.5 2.0 2.5 3.0 line regulation (%) output current (a) line regulation vs. output current (mic28303 - 1) vin = 12v to 50v v out = 5.0v f sw = 600khz 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 efficiency (%) output current (a) efficiency (vin = 12v) vs. output current (mic28303 - 1) 5.0v 3.3v 2.5v 1.8v 1.2v 0.8v f sw = 600khz ccm
micrel, inc. mic28303 february 12, 2015 9 revision 1.0 typical characteristics (continued) 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 efficiency (%) output current (a) efficiency (vin = 24v) vs. output current (mic28303 - 1) 5.0v 3.3v 2.5v 1.8v 1.2v 0.8v f sw = 600khz ccm 50 55 60 65 70 75 80 85 90 95 100 0.01 0.1 1 10 efficiency (%) output current (a) efficiency vs. output current (mic28303 - 1) v out = 12v f sw = 600khz ccm r3 = 23.2k 18vin 24vin 36vin 0 10 20 30 40 50 5 10 15 20 25 30 35 40 45 50 supply current (ma) input voltage (v) vin operating supply current vs. input voltage (mic28303 - 2) v out = 5v i out = 0a f sw = 600khz -1.0% -0.8% -0.6% -0.4% -0.2% 0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 7 12 17 22 27 32 37 42 47 output regulation (%) input voltage (v) output regulation vs. input voltage (mic28303 - 2) v out = 5.0v i out = 0a to 3a f sw = 600khz 0 5 10 15 20 25 30 35 40 45 50 5 10 15 20 25 30 35 40 45 50 shutdown current (a) input voltage (v) vin shutdown current vs. input voltage v en = 0v r16 = open f sw = 600khz 0 2 4 6 8 10 7 12 17 22 27 32 37 42 47 current limit (a) input voltage (v) output peak current limit vs. input voltage v out = 5.0v f sw = 600khz 400 450 500 550 600 650 700 750 800 7 12 17 22 27 32 37 42 47 switching frequency (khz) input voltage (v) switching frequency vs. input voltage v out = 5.0v i out = 2a 0.00 0.30 0.60 0.90 1.20 1.50 5 10 15 20 25 30 35 40 45 50 enable threshold (v) input voltage (v) enable threshold vs. input voltage falling rising f sw = 600khz 0 1 2 3 4 5 6 7 8 9 10 -50 -25 0 25 50 shutdown current (a) temperature ( c) vin shutdown current vs. temperature vin = 12v v en = 0v i out = 0a f sw = 600khz
micrel, inc. mic28303 february 12, 2015 10 revision 1.0 typical characteristics (continued) 0 2 4 6 8 10 -50 -25 0 25 50 75 100 125 current limit (a) temperature ( c) output peak current limit vs. temperature vin = 12v v out = 5.0v f sw = 600khz 0 20 40 60 80 100 -50 -25 0 25 50 75 100 125 en bias current (a) temperature ( c) en bias current vs. temperature vin = 12v v en = 0v f sw = 600khz 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 -50 -25 0 25 50 75 100 125 enable threshold (v) temperature ( c) enable threshold vs. temperature falling rising vin = 12v v out = 5v f sw = 600khz 0 4 8 12 16 20 24 28 32 36 40 -50 -25 0 25 50 75 100 125 supply current (ma) temperature ( c) vin operating supply current vs. temperature (mic28303 - 2) vin = 12v v out = 5.0v i out = 0a f sw = 600khz -0.3% -0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% -50 -25 0 25 50 75 100 125 load regulation (%) temperature ( c) load regulation vs. temperature (mic28303 - 2) vin = 12v v out = 5.0v i out = 0a to 3a f sw = 600khz -1.00% -0.50% 0.00% 0.50% 1.00% -50 -25 0 25 50 75 100 125 line regulation (%) temperature ( c) line regulation vs. temperature (mic28303 - 2) vin = 7v to 50v v out = 5.0v i out = 0a f sw = 600khz -1.0% -0.5% 0.0% 0.5% 1.0% -50 -25 0 25 50 75 100 125 line regulation (%) temperature ( c) line regulation vs. temperature (mic28303 - 2) vin = 7v to 50v v out = 5.0v i out = 0a f sw = 600khz 100 150 200 250 300 350 400 450 500 550 600 650 700 -50 -25 0 25 50 75 100 125 switching frequency (khz) temperature ( c) switching frequency vs. temperature (mic28303 - 2) vin = 12v v out = 5v i out = 0a 0.0% 0.1% 0.1% 0.2% 0.2% 0.3% 0.3% 0.4% 0.4% 0.0 0.5 1.0 1.5 2.0 2.5 3.0 line regulation (%) output current (a) line regulation vs. output current (mic28303 - 2) vin = 12v to 70v v out = 5.0v f sw = 600khz
micrel, inc. mic28303 february 12, 2015 11 revision 1.0 typical characteristics (continued) 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 3.5 4 efficiency (%) output current (a) efficiency (vin =12v) vs. output current (mic28303 - 2) 5.0v 3.3v 2.5v 1.8v 1.2v 0.8v f sw = 600khz 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 3.5 4 efficiency (%) output current (a) efficiency (vin = 24v) vs. output current (mic28303 - 2) 5.0v 3.3v 2.5v 1.8v 1.2v 0.8v f sw = 600khz 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 3.5 4 efficiency (%) output current (a) efficiency (vin = 38v) vs. output current (mic28303 - 2) 5.0v 3.3v 2.5v 1.8v 1.2v 0.8v f sw = 600khz 0 100 200 300 400 500 600 700 800 10.00 100.00 1000.00 10000.00 sw freq (khz) r19 (k) switching frequency v out = 5v i out = 2a vin = 12v 0 1 2 3 25 40 55 70 85 100 load current (a) maximum ambient temperature ( c) thermal derating (mic28303 - 2) v out = 5v f sw = 600khz t j_max = 125 c v in = 18v v in = 12v v in = 24v 0 1 2 3 25 40 55 70 85 100 load current (a) maximum ambient temperature ( c) thermal derating (mic28303 - 2) v out = 3.3v f sw = 600khz t j_max = 125 c v in = 18v v in = 12v v in = 24v 0 1 2 3 25 40 55 70 85 100 load current (a) maximum ambient temperature ( c) thermal derating (mic28303 - 2) v out = 2.5v f sw = 600khz t j_max = 125 c v in =18v v in = 12v v in = 24v 0 1 2 3 25 40 55 70 85 100 load current (a) maximum ambient temperature ( c) thermal derating (mic28303 - 2) v out = 1.8v f sw = 600khz t j_max = 125 c v in = 12v v in = 24v v in =18v
micrel, inc. mic28303 february 12, 2015 12 revision 1.0 functional characteristics ? 600khz switching frequency
micrel, inc. mic28303 february 12, 2015 13 revision 1.0 functional characteristics ? 600khz switching frequency (continued)
micrel, inc. mic28303 february 12, 2015 14 revision 1.0 functional characteristics ? 600khz switching frequency (continued)
micrel, inc. mic28303 february 12, 2015 15 revision 1.0 functional characteristics ? 600khz switching frequency (continued)
micrel, inc. mic28303 february 12, 2015 16 revision 1.0 functional characteristics ? 600khz switching frequency (continued)
micrel, inc. mic28303 february 12, 2015 17 revision 1.0 functional diagram
micrel, inc. mic28303 february 12, 2015 18 revision 1.0 functional description the mic28303 is an adaptive on - time synchronous buck regulator module built for high - input voltage to low - output voltage conversion applications. the mic28303 is designed to operate over a wide input voltage range, from 4.5v to 50v , and the output is adjustable with an external resistor divider. an adaptive on - time control scheme is employed to obtain a constant switching frequency and to simplify the control compensation. hiccup mode over - current protection is implemented by sensing low - side mosfet?s r ds(on) . the device features internal soft - start, enable, uvlo, and therma l shutdown. the module has integrated switching fets, inductor, bootstrap diode, resistor and capacitor. theory of operation per the functional diagram of the mic28303 module , t he output voltage is sensed by the mic28303 feedback pin fb via the voltage divider r1 and r11, and compared to a 0.8v reference voltage vref at the error comparator through a low - gain transconductance (gm) amplifier. if the feedback voltage decreases and the amplifier output is below 0.8v, then the error comparator will trigger the control logic and generate an on - time period. the on - time period length is predetermined by the ?fixed ton estimator? circuitry: sw in out ) estimated ( on f v v t = eq. 1 where v out is the output voltage, v in is the power stage input voltage, and f sw is the switching frequency. at the end of the on - time period, the internal high - side driver turns off the high - side mosfet and the low - side driver turns on the lo w - side mosfet. the off - time period length depends upon the feedback voltage in most cases. when the feedback voltage decreases and the output of the g m amplifier is below 0.8v, the on - time period is triggered and the off - time period ends. if the off - time p eriod determined by the feedback voltage is less than the minimum off - time t off(min) , which is about 200ns, the mic28303 control logic will apply the t off(min ) instead. t off(min) is required to maintain enough energy in the boost capacitor (c bst ) to drive the high - side mosfet. the maximum duty cycle is obtained from the 200ns t off(min) : s s ) min ( off s max t ns 200 1 t t t d ? = ? = eq. 2 w here : t s = 1/f sw . it is not recommended to use mic28303 with an off - time close to t off(min) during steady - state operation. the adaptive on - time control scheme results in a constant switching frequency in the mic28303 . the actual on - time and resulting switching frequency will vary with the different rising and falling times of the external mosfets. also, the minimum t on results in a lower switching frequency in high v in to v out applications. during load transients, the switching frequency is changed due to the varying off - time. to illustrate the control loop operation, both the steady - state and load transient sc enarios were analyzed . for easy analysis, the gain of the g m amplifier is assumed to be 1. with this assumption, the inverting input of the error comparator is the same as the feedback voltage. figure 1 shows the mic28303 control loop timing during steady - state operation. during steady - state, the g m amplifier senses the feedback voltage ripple, which is proportional to the output voltage ripple plus injected voltage ripple, to trigger the on - time period. the on - time is predetermined by the t on estimator . the termination of the off - time is controlled by the feedback voltage. at the valley of the feedback voltage ripple, which occurs when v fb falls below v ref , the off period ends and the next on - time period is triggered through the control logic circuitry.
micrel, inc. mic28303 february 12, 2015 19 revision 1.0 figure 1 . mic28303 control loop timing figure 2 shows the operation of the mic28303 during a load transient. the output voltage drops due to the sudden load increase, which causes the v fb to be less than v ref . this will cause the error comparator to trigger an on - time period. at the end of the on - time period, a minimum off - time t off(min) is generated to charge the bootstrap capacitor (c bst ) since the feedback voltage is still below v ref . then, the next on - time period is triggered due to the low feedback voltage. therefore, the switching frequency changes during the load transient, but returns to the nominal fixed frequency once the output has stabilized at the new load c urrent level. with the varying duty cycle and switching frequency, the output recovery time is fast and the output voltage deviation is small. figure 2 . mic28303 load transient response unlike true current - mode control, the mi c28303 uses the output voltage ripple to trigger an on - time period. the output voltage ripple is proportional to the inductor current ripple if the esr of the output capacitor is large enough. in order to meet the stability requirements, the mic28303 feedb ack voltage ripple should be in phase with the inductor current ripple and are large enough to be sensed by the g m amplifier and the error comparator. the recommended feedback voltage ripple is 20mv~100mv over full input voltage range. if a low esr output capacitor is selected, then the feedback voltage ripple may be too small to be sensed by the g m amplifier and the error comparator. also, the output voltage ripple and the feedback voltage ripple are not necessarily in phase with the inductor current rippl e if the esr of the output capacitor is very low. in these cases, ripple injection is required to ensure proper operation. please refer to ?ripple injection? subsection in application information for more details about the ripple injection technique. discontinuous mode ( mic28303 - 1 only) in continuous mode , the inductor current is always greater than zero; however, at light loads , the mic28303 - 1 is able to force the inductor current to operate in discontinuous mode. discontinuous mode is where the inductor current falls to zero , as indicated by trace (i l ) shown in figure 3 . during this period , the efficiency is optimized by shutting down all the non - essential circuits and minimizing the supply current. the mic28303 - 1 wakes up and turns on the high - side mosfet when the feedback voltage v fb drop s below 0.8v. the mic28303 - 1 has a zero c ross ing c omparator (zc) that monitors the inductor current by sensing the voltage drop across the low - side mosfet during its on - time. if the v fb > 0.8v and the inductor current goes slightly negative, then the mic28303 - 1 automatically powers down most of the ic circuitry and goes into a low - power mode. once the mic28303 - 1 goes into discontinuous mode, both dl and dh are low, which turns off the high - side and low - side mosfets. the load current is supplied by the output capacitors and v out drops. if the drop of v out causes v fb to go below v ref , then all the circuits will wake up into normal continuous mode. first , the b ias currents of most circuits reduced during the discontinuous mode are restored, and then a t on pulse is triggered before the drivers are turned on to avoid any possible glitches. finally, the high - side driver is turned on. figure 3 shows the control loop timing in discontinuous mode.
micrel, inc. mic28303 february 12, 2015 20 revision 1.0 figure 3 . mic28302 - 1 control loop timing (discontinuous mode) during discontinuous mode, the bias current of most circuits is substantially reduced. as a result, the total power supply current during discontinuous mode is only about 400 a, allowing the mic28303 - 1 to achieve high efficiency in light load applications. soft - start soft - start reduces the input power supply surge current at startup by controlling the output voltage rise time. the input surge appears while the output capacitor is charged up. a slower output rise time will draw a lower input surge current. the mic28303 implements an internal digital so ft - start by making the 0.8v reference voltage v ref ramp from 0 to 100% in about 5ms with 9.7mv steps. therefore, the output voltage is controlled to increase slowly by a stair - case v fb ramp. once the soft - start cycle ends, the related circuitry is disabled to reduce current consumption. pvdd must be powered up at the same time or after v in to make the soft - start function correctly. current limit the mic28303 uses the r ds(on) of the low side mosefet and external resistor connected from ilim pin to sw node to decide the current limit. figure 4 . mic28303 current - limiting circuit in each switching cycle of the mic28303 , the inductor current is sensed by monitori ng the low - side mosfet in the off period. the sensed voltage v(ilim) is compared with the power ground (pgnd) after a blanking time of 150ns . in this way the drop voltage over the resistor r15 (vcl) is compared with the drop over the bottom fet generating the short current limit. the small capacitor (c6) connected from ilim pin to pgnd filters the switching node ringing during the o ff- time allowing a better short limit measurement. the time constant created by r15 and c6 should be much less than the minimum off time. the v cl drop allows programming of short limit through the value of the resistor (r15), if the absolute value of the voltage drop on the bottom fet is greater than v cl . in that case the v(ilim) is lower than pgnd and a short circuit event is tri ggered. a hiccup cycle to treat the short event is generated. the hiccup sequence including the soft start reduces the stress on the switching fets and protects the load and supply for severe short conditions.
micrel, inc. mic28303 february 12, 2015 21 revision 1.0 the short - circuit current limit can be progra mmed by using equation 3 . ( ) cl cl ) on ( ds pp l clim i v r ) 5 . 0 i i ( r15 + d ? = eq. 3 where: i clim = desired c urrent limit r ds(on) = on - resistance of low - side power mosfet, p typically v cl = current - limit threshold ( typical absolute value is 14mv per the electrical characteristics ) i cl = current - limit source current ( typical value is 80a , per the electrical characteristics table) . ? i l(pp) = inductor current peak - to - peak, s ince the inductor is integrated use equation 4 to calculate the inductor ripple current. the peak - to - peak inductor current ripple is: l f v ) v (v v i sw in(max) out in(max) out l(pp) ? = d eq. 4 the mic28303 has 4.7h inductor integrated into the module. the typical value of r winding(dcr) of this particular lqgxfwrulvlqwkhudqjhrip in case of hard short, the short limit is folded down to allow an indefinite hard short on the output without any destructive effect. it is mandatory to make sure that the inductor current used to charge the output capacitance during soft start is under the folded short limit; otherwise the supply will go in hiccup mode and may not be finishing the soft start successfully. the mosfet r ds(on) varies 30 % to 40% with temperature; therefore, it is recommended to add a 50% margin to i clim in equation 3 to avoid false current limiting due to increased mosfet junction temperature rise. table 2 shows typical output current limit value for a given r15 with c6 = 10pf. table 2 . typical output current - limit value r15 typical output current limit 1.81k 3a 2.7k 6.3a
micrel, inc. mic28303 february 12, 2015 22 revision 1.0 application information simplified input transient circuitry the 5 6v absolute maximum rating of the mic28303 allows simplifying the transient voltage suppressor on the input supply side which is very common in industrial applications. the input supply voltage v in figure 5 may be operating at 12v input rail most of the time, but can encounter noise spike of 5 0v for a short duration. by using mic28303 , which has 5 6v absolute maximum voltage rating, the input transient suppressor is not needed. which saves on co mponent count, form factor, and ultimately the system becomes less expensive. figure 5 . simplified input transient circuitry setting the switching frequency the mic28303 switching frequency can be adjusted by changing the value of resistor r1 9 . the top resistor of 100k is internal to module and is connected between vin and freq pin, so the value of r19 sets the switching frequency. the switching frequency also depends upon vin, v out and load conditions. figure 6 . switching frequency adjustment equation 5 gives the estimated switching frequency: : u k 100 19 r 19 r f f o adj _ sw eq. 5 where: f o = switching f requency when r19 is open for more precise setting, it is recommended to use figure 7 : figure 7 . switching frequency vs. r19 output capacitor selection the type of the output capacitor is usually determined by the application and its equivalent series resistance (esr). voltage and rms current capability are two other important factors for selecting the output capacitor. recommended capacitor types are mlc c, tantalum, low - esr aluminum electrolytic, os - con and poscap. the output capacitor?s esr is usually the main cause of the output ripple. the mic28303 requires ripple injection and t he output capacitor esr e ffects the control loop from a stability point of view. 0 100 200 300 400 500 600 700 800 10.00 100.00 1000.00 10000.00 sw freq (khz) r19 (k ohm) switching frequency v out = 5v i out = 2a vin =48v vin = 12v
micrel, inc. mic28303 february 12, 2015 23 revision 1.0 the maximum value of esr is calculated as in equation 6 : l(pp) out(pp) c i v esr out d eq. 6 where: ? v out(pp) = peak - to - peak output voltage ripple i l(pp) = peak - to - peak inductor current ripple the total output ripple is a combination of the esr and output capacitance. the total ripple is calculated in equation 7 : 2 c l(pp) 2 sw out l(pp) out(pp) out esr i 8 f c i v + eq. 7 where: d = duty cycle c out = output capacitance value f sw = switching frequency as described in the ? theory of operation ? subsection in functional description , the mic28303 requires at least 20mv peak - to - peak ripple at the fb pin to make the g m amplifier and the error comparator behave properly. also, the output voltage ripple should be in phase wi th the inductor current. therefore, the output voltage ripple caused by the output capacitors value should be much smaller than the ripple caused by the output capacitor esr. if low - esr capacitors, such as ceramic capacitors, are selected as the output cap acitors, a ripple injection method should be applied to provide enough feedback voltage ripple. please refer to the ?ripple injection? subsection for more details. the voltage rating of the capacitor should be twice the output voltage for a tantalum and 20 % greater for aluminum electrolytic or os - con. the output capacitor rms current is calculated in equation 8 : 12 i i l(pp) (rms) c out eq. 8 the power dissipated in the output capacitor is: out out out c 2 (rms) c ) diss(c esr i p u eq. 9 input capacitor selection the input capacitor for the power stage input pv in should be selected for ripple current rating and voltage rating. tantalum input capacitors may fail when subjected to high inrush currents, caused by turning the input supply on. a tantalum input capacitor?s v oltage rating should be at least two times the maximum input voltage to maximize reliability. aluminum electrolytic, os - con, and multilayer polymer film capacitors can handle the higher inrush currents without voltage de - rating. the input voltage ripple wi ll primarily depend on the input capacitor?s esr. the peak input current is equal to the peak inductor current, so: v in = i l(pk) esr cin eq. 10 the input capacitor must be rated for the input current ripple. the rms value of input capacitor current is determined at the maximum output current. assuming the peak - to - peak inductor current ripple is low: d) (1 d i i out(max) cin(rms) u u | eq.11 the power dissipated in the input capacitor is: p diss(cin) = i cin(rms) 2 esr cin eq. 1 2 the general rule is to pick the capacitor with a ripple current rating equal to or greater than the calculated worst (v in_max ) case rms capacitor current. its voltage rating should be 20% to 50% higher than the maximum input voltage. typically the input ripple (dv) needs to be kept down to less than 10% of input voltage. the esr also increases the input ripple.
micrel, inc. mic28303 february 12, 2015 24 revision 1.0 equation 13 should be used to calculate the inp ut capacitor. also it is recommended to keep some margin on the calculated value: dv f ) d 1 ( i c sw out(max) in ? eq. 13 where : dv = t he input ripple and f sw is the switching frequency output voltage setting components the mic28303 requires two resistors to set the output voltage as shown in figure 8 : figure 8 . voltage - divider configuration the outpu t voltage is determined by equation 14: ? ? ? ? ? ? + = 11 1 1 v v fb out r r eq. 14 where: v fb = 0.8v a typical value of r1 used on the standard evaluation board is n ,i5lvwrrodujhlwpd\doorzqrlvhwreh introduced into the voltage feedback loop. if r1 is too small in value, it will decrease the efficiency of the power supply, especially at light loads. once r1 is selected, r 11 can be calculated using equa tion 15 : fb out fb v v r1 v r11 ? = eq. 15 ripple injection the v fb ripple required for proper operation of the mic28303 g m amplifier and error comparator is 20mv to 100mv. however, the output voltage ripple is generally designed as 1% to 2% of the output voltage. for a low output voltage, such as a 1v, the output voltage ripple is only 10mv to 20mv, and the feedback voltage ripple is less than 20mv. if the feedback voltage ripple is so small that the g m amplifier and error comparator cannot sense it, then the mic28303 will lose control and the output voltage is not regulated. in order to have some amount of v fb ripple, a ripple injection method is applied for low output voltage ripple applications. the table 2 summarizes the ripple injection component value s for ceramic output capacitor. the applications are divided into three situations according to the amount of the feedback voltage ripple: 1. enough ripple at the feedback voltage due to the large esr of the output capacitors ( figure 9 ): figure 9 . enough ripple at fb as shown in figure 10 , the converter is stabl e without any ripple injection. figure 10 . inadequate ripple at fb
micrel, inc. mic28303 february 12, 2015 25 revision 1.0 the feedback voltage ripple is: l(pp) c fb(pp) i esr r11 r1 r11 v out u u eq. 16 where: ?, l(pp) = t he peak - to - peak value of the inductor current ripple 2. inadequate ripple at the feedback voltage due to the small esr of the output capacitors , such is the case with ceramic output capacitor . the output voltage ripple is fed into the fb pin throug h a feed - forward capacitor c ff in this situation, as shown in figure 11 . the typical c ff value is between 1nf and 100nf. figure 11 . invisible ripple at fb with the feed - forward capacitor, the feedback voltage ripple is very close to the output voltage ripple: l(pp) fb(pp) ?, esr ?9 u | eq. 17 3. virtually no ripple at the fb pin voltage due to the very - lo w esr of the output capacitors. in this situation, the output voltage ripple is less than 20mv. therefore, additional ripple is injected into the fb pin from the switching node sw via a resistor r inj and a capacitor c inj , as shown in figure 11 . the injected ripple is: w u u u u u sw div in fb(pp) f 1 d) - (1 d k v ?9 eq. 18 r1//r11 r r1//r11 k inj div eq. 19 where : v in = p ower stage input voltage d = duty cycle f sw = switching frequency w = (r1// r 11 //r inj ) u c ff in equations 18 and 19 , it is assumed that the time constant associated with c ff must be much greater than the switching period: 1 t f 1 sw u w w eq. 20 if the voltage divider resistors r1 and r 11 duhlqwkhn range, then a c ff of 1nf to 10 0nf can easily satisfy the large time constant requirements. also, a 100nf injection capacitor c inj is used in order to be considered as short for a wide range of the frequencies. the process of sizing the ripple injection resistor and capacitors is: step 1. select c ff to feed all output ripples into the feedback pin and make sure the large time constant assumption is satisfied. typical choice of c ff is 1nf to 100nf if r1 and r 11 duhlqn udqjh step 2. select r inj according to the expected feedback volta ge ripple using equation 2 2 : d) (1 d f v ?9 k sw in fb(pp) div u u u w eq. 21 then the value of r inj is obtained as: 1) k 1 ( (r1//r11) r div inj u eq. 22 step 3. select c inj as 100nf, which could be considered as short for a wide range of the frequencies. table 3 summarizes t he typical value of components for particular input and output voltage, and 600khz switching frequency design, for details refer to the bill of materials section.
micrel, inc. mic28303 february 12, 2015 26 revision 1.0 table 3 . recommended component val ues for 600khz switching frequency v out vin r3 (r inj ) r1 (top feedback resistor ) r11 (bottom feedback resistor ) r19 c10 (c inj ) c12 (c ff ) c out 0.9v 5v to 50v 16.5k 10k 80.6k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 1.2v 5v to 50v 16.5k 10k 20k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 1.8v 5v to 50v 16.5k 10k 8.06k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 2.5v 5v to 50v 16.5k 10k 4.75k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 3.3v 5v to 50v 16.5k 10k 3.24k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 5v 7v to 50v 16.5k 10k 1.9k dnp 0.1f 2.2nf 47f/6.3v or 2 x 22f 12v 18v to 50v 23.2k 10k 715 dnp 0.1f 2.2nf 47f/16v or 2 x 22f thermal measurements and safe operating area measuring the ic?s case temperature is recommended to ensure it is within its operating limits. although this might seem like a very elementary task, it is easy to get erroneous results. the most common mistake is to use the standard thermal couple that comes with a thermal meter . this thermal couple wire gauge is large, typically 22 gauge, and behaves like a heatsink, resulting in a lower case measurement. two methods of temperature measurement are using a smaller thermal couple wire or an infrared thermometer. if a thermal coupl e wire is use d, it must be constructed of 36- gauge wire or higher (smaller wire size) to minimize the wire heat - sinking effect. in addition, the thermal couple tip must be covered in either thermal grease or thermal glue to make sure that the thermal coupl e junction is making good contact with the case of the ic. omega brand thermal couple (5sc - tt - k - 36- 36) is adequate for most applications. wherever possible, an infrared thermometer is recommended. the measurement spot size of most infrared thermometers is too large for an accurate reading on a small form factor ics. however, an ir thermometer from optris has a 1mm spot size, which makes it a good choice for measuring the hottest point on the case. an optional stand makes it easy to hold the beam on the ic for long periods of time. the safe operating a rea (soa) of the mic28303 is shown in the typical characteristics 275khz switching frequency section . these t hermal measurements were taken on mic28303 evaluation board. since the mic28303 is an entire system comprised of s witching regulator c ontroller, mosfets and i nductor, the part needs to be considered as a system. the soa curves will give guidance to reasonable use of the mic28303 . emission characteristics of mic28303 the mic28303 integrates switching components in a single package, so the mic28303 has reduced emission compared to standard buck regulator with external mosfets and inductors. the radiated emi scans for mic28303 are shown in the typical characteristics section . the lim it on the graph is per en55022 c lass b standard.
micrel, inc. mic28303 february 12, 2015 27 revision 1.0 pcb layout guidelines warning: to minimize emi and output noise, follow these layout recommendations. pcb l ayout is critical to achieve reliable, stable and efficient performance. a ground plane is required to control emi and minimize the inductance in power, signal and return paths. the following figures optimized from small form factor point of view shows top and bottom layer of a four layer pcb . it is recommended to use mid layer 1 as a continuous ground plane. figure 12 . top and b ottom layer of a four - layer board the following guidelines should be followed to insure proper oper ation of the mic28303 converter: ic ? the analog ground pin (gnd) must be connected directly to the ground planes. do not route the gnd pin to the pgnd pin on the top layer. ? place the ic close to the point of load (pol). ? use fat traces to route the input and output power lines. ? analog and power grounds should be kept separate and connected at only one location. input capacitor ? place the input capacitors on the same side of the board and as close to the ic as possible. ? place several vias to the ground plane close to the input capacitor ground terminal. ? use either x7r or x5r dielectric input capacitors. do not use y5v or z5u type capacitors. ? do not replace the ceramic input capacitor with any other type of capacitor. any type of capacitor can be placed in parallel with the input capacitor. ? if a tantalum input capacitor is placed in parallel wi th the input capacitor, it must be recommended for switching regulator applications and the operating voltage must be derated by 50%. ? in ?hot - plug? applications, a tantalum or electrolytic bypass capacitor must be used to limit the over - voltage spike seen on the input supply with power is suddenly applied. rc snubber ? place the rc snubber on the same side of the board and as close to the sw pin as possible. sw node ? do not route any digital lines underneath or close to the sw node. ? keep the switch node (sw) away from the feedback (fb) pin. output capacitor ? use a wide trace to connect the output capacitor ground terminal to the input capacitor ground terminal. ? phase margin will change as the output capacitor value and esr changes. contact the factory if the o utput capacitor is different from what is shown in the bom. ? the feedback trace should be separate from the power trace and connected as close as possible to the output capacitor. sensing a long high - current load trace can degrade the dc load regulation.
micrel, inc. mic28303 february 12, 2015 28 revision 1.0 typical application schematic figure 13 . typical application schematic of mic28303
micrel, inc. mic28303 february 12, 2015 29 revision 1.0 bill of materials item part number manufacturer description qty . c1 eeu - fc2a101 panasonic ( 6 ) 100f aluminum capacitor, 100v 1 c2, c3 grm32er72a225k murata ( 7 ) 2.2f/100v ceramic capacitor, x7r, size 1210 2 c3225x7r2a225k tdk ( 8 ) 12101c225kat2a avx ( 9 ) c6 gcm1885c2a100ja16d murata 10pf, 100v, 0603, npo 1 06031a100jat2a avx c12 grm188r72a222ka01d murata 2.2nf/100v ceramic capacitor, x7r, size 0603 1 06031c222kat2a avx c1608x7r2a222k tdk c14 grm31cr60j476me19k murata 47f/6.3v ceramic capacitor, x5r, size 1210 1 12106d476mat2a avx c10 grm188r71h104ka93d murata 0.1f/6.3v ceramic capacitor, x7r, size 0603 1 06035c104kat2a avx c1608x7r1h104k tdk r1 crcw060310k0fkea vishay dale ( 10 ) 10k resistor, size 0603, 1% 1 r3 crcw06031652f vishay dale 16.5k resistor, size 0603, 1% 1 r11 crcw06031k91fkea vishay dale 1.91k resistor, size 0603, 1% 1 r15 crcw06033k57fkea vishay dale 3.57k resistor, size 0603, 1% 1 r19 crcw060375k0fkea vishay dale 75k resistor, size 0603, 1% 1 u1 mic28303 - 1ym p micrel, inc. ( 11) 50v , 3a power module 1 mic28303 - 2ym p notes: 6. panasonic: www.panasonic.com . 7. murata: www.murata.com . 8. tdk: www.tdk.com . 9. avx: www.avx.com . 10. vishay: www.vishay.com . 11. micrel, inc.: www.micrel.com .
micrel, inc. mic28303 february 12, 2015 30 revision 1.0 package information ( 12) 64- pin 12mm 12mm qfn ( mp ) note: 12. package information is correct as of the publication date. for updates and most cu rrent information, go to www.micrel.com .
micrel, inc. mic28303 february 12, 2015 31 revision 1.0 recommended land pattern
micrel, inc. mic28303 february 12, 2015 32 revision 1.0 recommended land pattern (continued)
micrel, inc. mic28303 february 12, 2015 33 revision 1.0 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944 - 0800 fax +1 (408) 474- 1000 web http://www.micrel.com micrel, inc. is a leading global manufacturer of ic solutions for the worldwide high performance linear and power, lan, and t iming & communications markets. the company?s products include advanced mixed - signal, analog & power semiconductors; high - performance communication, clock management, mems - based clock oscillators & crystal - less clock generators, ethernet switches, and physical la yer transceiver ics. company customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and comp uter products. corporation headquarters and state - of - the - art wafer fabrication facilities are located in san jose, ca, with regional sales and support offices and advanced technology design centers situated throughout the americas, europe, and asia. additionally, the company maintains a n extensive network of distributors and reps worldwide. micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this datasheet. this information is not intended as a warranty and micrel does not assume responsibility for its use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel or oth erwise, to any intellectual property rights is granted by this document. except as provided in micrel?s terms and conditions of sale for such products, micrel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where mal function of a product c an reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are i ntended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. a purchaser?s use or sale of micrel products for use in life support appliances, devices or systems is a purchaser?s own risk a nd purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale . ? 20 1 5 micrel, incorporated.

▲Up To Search▲

Price & Availability of MIC28303-2YMP

	To Download MIC28303-2YMP Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .